Three B vitamins are involved in what is known as 1-carbon metabolism. This is the movement of 1 carbon units, generally methyl groups (CH3). It is similar to the movement of the amino group that occurs in transamination. As shown in the figure below, folate, vitamin B12, and vitamin B6 are the B vitamins involved in 1-carbon metabolism.
Figure 11.1 One-carbon metabolism depiction. 5-methyl tetrahydrofolate (THF) donates a methyl group to cobalamin forming methylcobalamin. Methylcobalamin donates a methyl group to homocysteine, forming methionine (amino acid). Alternatively, vitamin B6 can be utilized to convert homocysteine into cysteine.
Vitamin B6 has been covered already in the previous chapter, so this chapter is going to focus on folate and vitamin B12. We will examine this figure in pieces, so that hopefully by the time this chapter is completed, you will understand the role of all these vitamins in 1-carbon metabolism.
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